$ echo -n -e \ "wx8888888888888888\n1414561699\n5K8264ILTKCH16CQ2502SI8ZNMTM67VS\nprepay_id=wx201410272009395522657a690389285100\n" \ | openssl dgst -sha256 -sign apiclient_key.pem \ | openssl base64 -A 将这串命令行转换为java代码

以下是将命令行转换为Java代码的示例：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

public class Sign {
    public static void main(String[] args) throws Exception {
        String data = "wx8888888888888888\n1414561699\n5K8264ILTKCH16CQ2502SI8ZNMTM67VS\nprepay_id=wx201410272009395522657a690389285100\n";
        byte[] keyBytes = loadPrivateKey("apiclient_key.pem");
        PrivateKey privateKey = KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(keyBytes));
        byte[] signature = signSHA256withRSA(privateKey, data.getBytes());
        System.out.println(Base64.encodeBase64String(signature));
    }

    private static byte[] loadPrivateKey(String fileName) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader(fileName));
        StringBuilder builder = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            if (!line.startsWith("-----")) {
                builder.append(line);
            }
        }
        reader.close();
        return Base64.decodeBase64(builder.toString());
    }

    private static byte[] signSHA256withRSA(PrivateKey privateKey, byte[] data) throws Exception {
        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(new SecretKeySpec(privateKey.getEncoded(), "HmacSHA256"));
        return mac.doFinal(data);
    }
}

注意：这只是一个示例代码，需要根据实际情况进行修改和调整。同时，需要将`apiclient_key.pem`文件放在当前目录下。